We propose to develop a revolutionary breast cancer diagnostic device that is minimally invasive, has the potential to be as accurate as a core biopsy, cost effective, and provides the physician with an immediate diagnosis. Our device measures the optical and electrical properties of tissue near the distal tip of a 20 gauge needle probe at 100 Hz. By combining proven measurements such as optical spectroscopy, fluorescence and electrical impedance we expect to significantly increase the specificity and sensitivity of these individual techniques. In normal use each probe insertion acquires multiple measurements through normal and suspicious tissue providing both microscopic and macroscopic information about the lesion. Effectively each insertion provides detailed measurements for a cylinder of tissue approximately 1 mm in diameter and length of the insertion. Since the probe records the depth simultaneously with the other measurements structural differences can be detected that could play an important role in improving the overall accuracy. For example, the change in blood oxygen from the boundary of a tumor to the center can be measured. Detailed measurements in normal and suspicious tissue also allow patient-to-patient variations to be considered in the data analysis.